This invention relates to the precision control of the flow of fluids through flexible conduits and, more particularly, to the control of fluid flow through tubing used in biomedical application.
In biomedical practice the flow of therapeutic and other fluids to a patient is controlled using various clamps which typically have an "on" and "off" position.
Since biomedical fluids are usually applied through plastic tubing, the clamps often hold their positions with difficulty. This is because the compression of a plastic tube to terminate flow produces stress within the tubing that applies counterforce to the closing element. In some cases the counterforce is sufficient to open a clamp that has been set into a closed position.
In addition, the application of pinching forces to plastic tubing tends to produce distortion and flattening of the tubing. This not only can interfere with the flow of fluid, the clamp positions can create weaknesses and subsequent failure in the tubing.
Another difficulty with conventional flow control clamps is that they are imprecise in adjustment. Not only is it difficult to arrive at a setting for a prescribed flow rate, once a desired setting is attained, it is difficult to hold because of the counterpressure applied as a result of the compressive force applied to the tubing, and because of the naturally low coefficient of friction associated with plastic materials.
Even in cases where attempts have been made to guard against inadvertent movement of the flow control device, the techniques that have been employed generally rely upon a ratchet with a rotatable member such that inadvertent force on the tubing, for example when a patient moves, can dislodge and alter the flow control setting of the device.
Illustrative examples of the prior art include: Tersteegen U.S. Pat. No. 4,429,852 "Adapter"; Stephens U.S. Pat. No. 4,193,174 "Lever and Fulcrum Clamping Assembly"; McGrath U.S. Pat. No. 4,380,103 "Balloon Clip"; MacNeil U.S. Pat. No. 4,346,869 "Tube Clamp".
Other illustrative examples of the prior art are set forth in the tabulation below:
__________________________________________________________________________ U.S. Pat. No. & Patentee & (Issue Date (Title) Assignee __________________________________________________________________________ 4,911,399 Green Anglo-American, Inc. (3/27/90) (Cam Valve for Regulation of Fluid Flow Through Flexible Tubing) 4,337,791 Tech et al La-Van Tech Development (7/6/82) (Flow Control Regulator) Corp. 4,335,866 Bujan Abbott Laboratories (6/22/82) (Flow Control Device) 4,247,076 Larkin Abbott Laboratories (1/27/81) (Toggle Action Tubing Clamp) 3,984,081 Hoganson The Raymond Lee (10/5/76) (Medical Device for Organization, Inc. Controlling Flow of Intravenous Solutions) 3,960,149 Bujan Abbott Laboratories (6/1/76) (Flow Control Device) 3,847,370 Engelscher Horizon Industries Ltd. (11/12/74) (Tubing Servicing Device) 3,802,463 Dabney Cutter Laboratories, (4/9/74) (Flow Control Apparatus) Inc. 3,612,474 Strohl, Jr. Abbott Laboratories (10/12/71) (Flow Control Device for Flexible Tubes) 3,329,391 Deane (7/4/67) (Surgical Pinch Valve) 3,215,395 Gorbar (11/2/65) (Regulating Clamp for Flexible Tubes) 3,135,259 Evans Sterilon Corp., (6/2/64) (Infusion Flow Control Valve) 3,099,429 Broman Baxter Laboratories, (7/30/63) (Roller Clamp for Inc. Parenteral Solution Equipment) 2,595,511 Butler (5/6/52) (Pinch Valve) 1,330,523 Evitts et al (10/20) (Tube Clamp) __________________________________________________________________________
Although a number of clamping devices with serrations for positioning a clamp against a flexible tube are in the prior art, none of these provide the security against inadvertent movement of the tubing with respect to its housing as needed in modern biomedical procedures.
Accordingly, it is an object of the invention to promote the control over the flow of fluids through conduits, particularly for biomedical applications. A related object is to enhance the amount of control that can be exercised in the case of flow through plastic tubing.
Another object of the invention is to achieve precision control over the amount of fluid flow and permit accurate adjustment over the amount of fluid flow and permit accurate adjustment over the amount of flow. A related object is to achieve this kind of precision in the case of biomedical fluids applied through plastic tubing.